Semiconductor device and method for manufacturing semiconductor device

A method for manufacturing a semiconductor device,

• the method comprising:
• a first forming step of selectively forming an insulator on one of main surfaces of a first conductivity-type semiconductor substrate constituting a first conductivity-type drift layer;
• a second forming step of selectively forming a second conductivity-type well region on one of the main surfaces of the first conductivity-type semiconductor substrate by implanting ions of a second conductivity-type impurity, with the insulator serving as a mask, and diffusing the second conductivity-type impurity by heat treatment;
• a first mask forming step of forming a first resist mask that has a first opening for selectively exposing the second conductivity-type well region between the insulator and the first resist mask;
• an ion implantation step of ion-implanting successively two types of first conductivity-type impurities having mutually different diffusion coefficients, into the second conductivity-type well region through the first opening by using the insulator and the first resist mask as masks;
• an annealing step of forming a first conductivity-type source region and a second conductivity-type low-impurity-concentration region by diffusing the two types of first conductivity-type impurities having mutually different diffusion coefficients by means of annealing;
• a third forming step of forming a gate insulator on one of the main surfaces of the first conductivity-type semiconductor substrate;
• and
• a fourth forming step of forming a gate electrode on surfaces of the first conductivity-type source region, the second conductivity-type low-impurity-concentration region, the second conductivity-type well region, and the first conductivity-type drift layer, with the gate insulator interposed between the gate electrode and the surfaces.

A method for manufacturing a semiconductor device,

• the method comprising:
• a first forming step of forming a gate insulator on one of main surfaces of a first conductivity-type semiconductor substrate;
• a second forming step of forming a gate electrode on a surface of the gate insulator by patterning a polysilicon film;
• a third forming step of selectively forming a second conductivity-type well region on one of the main surfaces of the first conductivity-type semiconductor substrate by ion-implanting a second conductivity-type impurity, with the gate electrode serving as a mask, and diffusing the second conductivity-type impurity by heat;
• a first mask forming step of forming a first resist mask that has a first opening for selectively exposing the second conductivity-type well region between the gate electrode and the first resist mask;
• an ion implantation step of ion-implanting two types of first conductivity-type impurities having mutually different diffusion coefficients, into the second conductivity-type well region through the first opening by using the gate electrode and the first resist mask as masks;
• and
• a fourth forming step of forming a first conductivity-type source region and a second conductivity-type low-impurity-concentration region by diffusing the two types of first conductivity-type impurities having mutually different diffusion coefficients by means of annealing.

A semiconductor device, comprising:

• a layer of a first conductivity type;
• a well region of a second conductivity type formed in the layer;
• a source region of the first conductivity type formed on a surface of the well region;
• and
• an adjacent region formed adjacent to the source region, between the source region and the well region;
• wherein the adjacent region has an impurity concentration lower than an impurity concentration of the well region.